Controlling fragmentation of chemically strengthened glass

Abstract

A method of manufacturing a glass substrate to control the fragmentation characteristics by etching and filling trenches in the glass substrate is disclosed. An etching pattern may be determined. The etching pattern may outline where trenches will be etched into a surface of the glass substrate. The etching pattern may be configured so that the glass substrate, when fractured, has a smaller fragmentation size than chemically strengthened glass that has not been etched. A mask may be created in accordance with the etching pattern, and the mask may be applied to a surface of the glass substrate. The surface of the glass substrate may then be etched to create trenches. A filler material may be deposited into the trenches.

What is claimed is: 
     
       1. A method of manufacturing a glass substrate to control fragmentation characteristics of the glass substrate, the method comprising:
 determining an etching pattern, the etching pattern being configured to control a fragmentation size of a glass substrate by modifying a stress field within the glass substrate to create an inhomogeneous stress field; 
 masking a first surface of the glass substrate according to the etching pattern, the glass substrate being chemically strengthened glass, the glass substrate having an exterior region and an interior region, wherein the exterior region has residual compressive stresses and the interior region has residual tensile stresses; 
 etching an unmasked portion of the first surface to produce a plurality of trenches in the first surface; and 
 filling the plurality of trenches with a filler material to generate the inhomogeneous stress field in the glass substrate, wherein the filler material is a composition of a first material and a second material, the composition having a first volume, wherein the composition of the first material and the second material, when heated, experiences a chemical reaction to create one or more products, the one or more products combined having a second volume, and wherein the second volume is smaller than the first volume. 
 
     
     
       2. The method of  claim 1 , wherein a metal filament is inserted into the composition of the first material and the second material, the method further comprising:
 determining that the chemical reaction should be initiated; and 
 running a current through the metal filament, wherein the current is large enough to cause the metal filament heat up to a temperature sufficient to initiate the chemical reaction between the first material and the second material. 
 
     
     
       3. The method of  claim 1 , wherein the composition further includes a third material. 
     
     
       4. The method of  claim 3 , wherein the third material is a catalyst for the chemical reaction between the first material and the second material. 
     
     
       5. The method of  claim 1 , wherein the first material is elemental aluminum and the second material is elemental nickel. 
     
     
       6. The method of  claim 1 , wherein the filling the plurality of trenches comprises layering the first material and the second material inside the plurality of holes. 
     
     
       7. The method of  claim 1 , wherein the fragmentation size of the glass substrate is less than 250 micrometers, the fragmentation size being an average of a width of a plurality of fragments created when the glass substrate fractures. 
     
     
       8. The method of  claim 1 , the method further comprising bonding the glass substrate to a second glass substrate. 
     
     
       9. The method of  claim 1 , wherein the etching pattern and filler material are selected to minimize the fragmentation size of the glass substrate. 
     
     
       10. The method of  claim 1 , wherein the etching pattern includes two or more parallel trenches. 
     
     
       11. The method of  claim 10 , wherein the determining the etching pattern includes determining an amount of space between each of the two or more parallel trenches. 
     
     
       12. The method of  claim 10 , wherein the determining the etching pattern include determining a width of each of the two or more parallel trenches. 
     
     
       13. The method of  claim 3 , wherein the third material is an oxide. 
     
     
       14. A method of manufacturing a glass substrate to control fragmentation characteristics of the glass substrate, the method comprising:
 determining an etching pattern, the etching pattern being configured to control a fragmentation size of a glass substrate by modifying a stress field within the glass substrate to create an inhomogeneous stress field; 
 masking a first surface of the glass substrate according to the etching pattern, the glass substrate being chemically strengthened glass, the glass substrate having an exterior region and an interior region, wherein the exterior region has residual compressive stresses and the interior region has residual tensile stresses; 
 etching an unmasked portion of the first surface to produce a plurality of trenches in the first surface; and 
 filling the plurality of trenches with a metal having a thermal expansion coefficient greater than the thermal expansion coefficient of the glass substrate and a Young's modulus that is greater than the Young's modulus of the glass substrate to generate the inhomogeneous stress field in the glass substrate by:
 depositing the metal on the first surface after the first surface has been etched; and 
 polishing the first surface to remove any metal that is on the first surface and not in a trench. 
 
 
     
     
       15. The method of  claim 14 , wherein the fragmentation size of the glass substrate is less than 250 micrometers, the fragmentation size being an average of a width of a plurality of fragments created when the glass substrate fractures. 
     
     
       16. The method of  claim 14 , the method further comprising bonding the glass substrate to a second glass substrate. 
     
     
       17. The method of  claim 14 , wherein the metal is aluminum. 
     
     
       18. The method of  claim 14 , wherein the etching pattern and filler material are selected to minimize the fragmentation size of the glass substrate. 
     
     
       19. The method of  claim 14 , wherein the etching pattern includes one or more disconnected features, the one or more disconnected features being defined by the plurality of trenches. 
     
     
       20. The method of  claim 19 , wherein the one or more disconnected features include trenches in a rectangular configuration.